The object of the proposed research is to develop mammalian cells in vitro, which overproduce oxygen radicals and therefore can be used as model systems for studying oxygen radical effects and methods of protecting against oxygen radical damages. The cell lines will be developed by constructing vectors containing cDNAs which code for oxygen radical producing enzymes and then transfecting the vectors into the human lymphoblastoid cell line AHH-1. The cDNAs will be under the control of regulatable promoters so that the levels of oxygen radical production can be regulated. These cell lines will then be used to study the effects of oxygen radicals on various cellular processes, including DNA damage and to identify agents which protect against oxygen radical damage.